Invalidate paint properties on paint offset changes

third_party/WebKit/Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 307 matching lines @@
   updateBackgroundAttachmentFixedStatusAfterStyleChange();
 
   if (oldStyle) {
     LayoutFlowThread* flowThread = flowThreadContainingBlock();
     if (flowThread && flowThread != this)
       flowThread->flowThreadDescendantStyleDidChange(this, diff, *oldStyle);
 
     updateScrollSnapMappingAfterStyleChange(&newStyle, oldStyle);
   }
 
+  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
+    // The overflow clip paint property depends on border sizes through
+    // overflowClipRect(), so we trigger a property update if any border is or
+    // was present. This check could be more precise (checking the actual
+    // border values) if performance is an issue.
+    if (hasOverflowClip() || styleRef().containsPaint() || hasControlClip()) {
+      if (newStyle.hasBorder() || (oldStyle && oldStyle->hasBorder()))

[Xianzhu, 2016/12/05 16:55:53]

How does it work if overflow clip changed without a border?

+        setNeedsPaintPropertyUpdate();
+    }
+  }
+
   // Non-atomic inlines should be LayoutInline or LayoutText, not LayoutBox.
   DCHECK(!isInline() || isAtomicInlineLevel());
 }
 
 void LayoutBox::updateBackgroundAttachmentFixedStatusAfterStyleChange() {
   if (!frameView())
     return;
 
   // On low-powered/mobile devices, preventing blitting on a scroll can cause
   // noticeable delays when scrolling a page with a fixed background image. As
@@ skipping 1347 matching lines @@
 
 void LayoutBox::frameRectChanged() {
   if (node() && node()->isElementNode()) {
     Element& element = toElement(*node());
     element.setNeedsResizeObserverUpdate();
   }
   // The frame rect may change because of layout of other objects.
   // Should check this object for paint invalidation.
   if (!needsLayout())
     setMayNeedPaintInvalidation();
+
+  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
+    // The overflow clip paint property depends on the border box rect through
+    // overflowClipRect, which in turn depends on the frame rect.
+    if (hasOverflowClip() || styleRef().containsPaint() || hasControlClip())
+      setNeedsPaintPropertyUpdate();
+  }
 }
 
 bool LayoutBox::intersectsVisibleViewport() const {
   LayoutRect rect = visualOverflowRect();
   LayoutView* layoutView = view();
   while (!layoutView->frame()->ownerLayoutItem().isNull())
     layoutView =
         LayoutAPIShim::layoutObjectFrom(layoutView->frame()->ownerLayoutItem())
             ->view();
   mapToVisualRectInAncestorSpace(layoutView, rect);
@@ skipping 3918 matching lines @@
   LayoutRect rect = frameRect();
 
   LayoutBlock* block = containingBlock();
   if (block)
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 }  // namespace blink